A new method of capturing detailed, three-dimensional images of minute samples of material under extreme pressures is shedding light on the evolution of the Earth's interior. Early results suggest that the early Earth did not have to be entirely molten to separate into the rocky crust and iron-rich core it has today. Researchers at Stanford University and SLAC National Accelerator Laboratory are leading the group pioneering the technique, which could lead to a wide range of new experiments.
To answer the big questions, it often helps to look at the smallest details.That is the approach Stanford mineral physicist Wendy Mao is taking to understanding a major event in Earth's inner history. Using a new technique to scrutinize how minute amounts of iron and silicate minerals interact at ultra-high pressures and temperatures, she is gaining insight into the biggest transformation Earth has ever undergone -- the separation of its rocky mantle from its iron-rich core approximately 4.5 billion years ago.
The technique, called high-pressure nanoscale X-ray computed tomography, is being developed at SLAC National Accelerator Laboratory. With it, Mao is getting unprecedented detail -- in three-dimensional images -- of changes in the texture and shape of molten iron and solid silicate minerals as they respond to the same intense pressures and temperatures found deep in the Earth.
Mao will present the results of the first few experiments with the technique at the annual meeting of the American Geophysical Union in San Francisco on Dec. 16.
Tomography refers to the process that creates a three-dimensional image by combining a series of two-dimensional images, or cross-sections, through an object. A computer program interpolates between the images to flesh out a recreation of the object.
Researchers at SLAC have developed a way to combine a diamond anvil cell, which compresses tiny samples between the tips of two diamonds, with nanoscale X-ray computed tomography to capture images of material at high pressure. The pressures deep in the Earth are so high -- millions of times atmospheric pressure -- that only diamonds can exert the needed pressure without breaking under the force.
At present, the SLAC researchers and their collaborators from HPSync, the High Pressure Synergetic Consortium at the Advanced Photon Source at Argonne National Laboratory, are the only group using this technique.
"It is pretty exciting, being able to measure the interactions of iron and silicate materials at very high pressures and temperatures, which you could not do before," said Mao, an assistant professor of geological and environmental sciences and of photon science. "No one has ever imaged these sorts of changes at these very high pressures."
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Edited by ShatteringBlue - 12/19/10 at 10:26am